Currently, motor vehicles are equipped with signal lamps designed to emit a light beam during reduced visibility conditions, e.g., in case of fog or heavy rain. Such signal lamps can be integrated in the body as separate lighting elements or they can be an integral part of headlights and tail lights in the form of a partial lighting unit. Lighting units for fog lights provide a short light ray of the white or red color, which helps to light through fog, heavy rain or snowfall. The front/white fog light illuminates the space directly in front of the vehicle while the red/rear fog light enhances road traffic safety, helping to improve visibility of the respective vehicle for the other participants of road traffic.
The patent documents EP0322370, GB2041189B, EP0404990, and DE19951407 disclose designs of rear fog lamps comprising an assembly of various optical elements, e.g., in the form of a ball lens, Fresnel lens, reflective surfaces, prisms, collimators etc., the resulting light pattern/trace with a rhombic shape being composed on the display surface by means of individual optical elements. Each optical element directs light rays to a certain partial area of the resulting light trace and creates a partial pattern. A disadvantage of the prior art is the fact that to arrange the light beam to a rhombic shape and to meet photometric requirements, very powerful light sources must be used, which is consequently manifested by higher financial costs. Another disadvantage is the fact that if the light trace consists of partial patterns, a small production defect of a partial optical element is manifested in the final light trace where the partial pattern corresponding to the defective optical element will be deformed.
The object of the invention is to design an optical system for motor vehicles adapted to create a light beam for lighting at a reduced visibility that has low requirements for installation in the vehicle body, ensures high efficiency of the optical system and enables to create a light pattern of an approximately rhombic shape on the display surface by means of optical elements.